Chapter 69 Seizure Disorders
PATHOPHYSIOLOGY
A seizure is a sudden, transient alteration in brain function as a result of abnormal neuronal activity and excessive cerebral electrical discharge. This activity can be partial or focal, originating in a specific area of the cerebral cortex—or generalized, involving both hemispheres of the brain. It is indicative of underlying brain pathology. Clinical manifestations vary, depending on the area(s) of brain involvement. The types of seizure affecting children and adolescents are listed in Box 69-1, which is the international classification of epileptic seizures created in 1981 by the International League Against Epilepsy. This classification is currently being revised.
Box 69-1 The International Classification of Epileptic Seizures
I. Partial (focal, local) seizures
II. Generalized seizures (convulsive or nonconvulsive, all associated with loss of consciousness)
III. Unclassified epileptic seizures—cannot be classified because of inadequate or incomplete data; includes some neonatal seizures (e.g., rhythmic eye movements, chewing, and swimming movements)
Adapted from Commission on Classification and Terminology of the International League Against Epilepsy. Proposal for revised clinical and electroencephalographic classification of epileptic seizures. Epilepsia 22:489–501, 1981 currently under revision (p. 20, Dreifuss, 1996).
If an area of the brain is affected, a focal seizure occurs, and if the whole brain is affected, a generalized seizure occurs. Any type of seizure can secondarily generalize. Before a focal seizure, a person may have a preictal (preseizure) phase consisting of varied symptoms, which may include a feeling, a subjective sensation, or a physical symptom signifying that a seizure will occur. In younger children the preictal phase may consist of a mood change or clingy type behavior that the parent will say occurs before the seizure.
A seizure is referred to as the ictal phase. Most seizures last less than 5 minutes, the majority less than 2 minutes. Seizure symptoms can include vocal, motor, cognitive, respiratory, and autonomic components, change in consciousness, and/or loss of consciousness. The postictal phase may occur after the seizure, and symptoms may include headache, fatigue, confusion, transient focal weakness (Todd’s paresis or paralysis), speech difficulty, amnesia, muscle aches, sleepiness, and so forth. Seizures can be further classified as idopathic if there is not identifiable cause, symptomatic if a cause is identified, or cryptogenic if an unidentified brain disorder is suspected.
The causes of seizure include perinatal factors, anoxia, congenital malformations of the brain, genetic factors, infectious disease (encephalitis, meningitis), febrile illness, metabolic disorders, trauma, neoplasms, toxins, circulatory disturbances, and degenerative diseases of the nervous system. Seizure triggers can include sleep deprivation, poor nutrition and hydration, photic stimulation, nonadherence to aspects of the treatment plan, stress, illness, certain medications, hormonal issues, and alcohol or drug use or withdrawal.
Epilepsy is a disorder characterized by recurrent, spontaneous, unprovoked seizures that are primarily of cerebral origin; it indicates the presence of underlying brain dysfunction. Epilepsy is not a disease in itself but a disorder, which can include possible effects on functional status, social status, emotional status, cognition, perception of health status, and quality of life. When a person is diagnosed with epilepsy, the seizure is classified according to type. Once the seizure type is known, the age of onset and the medical history, including development, physical examination, and electroencephalogram (EEG) pattern, are used to determine if the epilepsy fits into an epilepsy syndrome. Epilepsy syndromes common in children include juvenile absence epilepsy, benign centrotemporal epilepsy, and juvenile myoclonic epilepsy. Other disorders have clinical symptoms that can look like seizures. It is important to distinguish seizures from breath-holding spells, behavior disorders, cardiac arrrhythmias, anxiety attacks, migraine disorder, movement disorders, nonepileptic seizures, sleep disorders, and syncope.
INCIDENCE
1. Epilepsy and seizures affect 2.5 million Americans of all ages.
2. Of the general population, 10% will experience a seizure at some time in their life.
3. Of the American population, 3% will develop epilepsy by 75 years of age.
4. Epilepsy incidence is highest in those under 2 years and over 65 years of age.
5. Each year 45,000 children under age 15 years develop epilepsy.
6. Infections and metabolic disorders are the most common causes of seizure in children.
7. Etiology of epilepsy is unknown in two thirds of affected individuals.
8. Of all children between 6 months and 5 years of age, 2% to 5% will experience a febrile seizure.
9. Of children with febrile seizures, 2% to 5% will develop epilepsy.
CLINICAL MANIFESTATIONS
See Box 69-1 for clinical manifestations of seizure activity. Seizure disorders may also affect cognitive and functional abilities and emotional status during nonseizure periods.
COMPLICATIONS
Of Epilepsy
1. Cognition: learning disabilities
2. Neurodevelopmental: attention deficit or attention deficit/hyperactivity disorders (ADD/ADHD); speech, gross motor, and fine motor disorders
3. Neurologic: headache, migraines, sudden unexplained death in epilepsy [SUDEP]
4. Psychiatric: behavioral, anxiety-depressive disorders
5. Social challenges: stigma, school or job performance, driving restrictions (different in each state)
LABORATORY AND DIAGNOSTIC TESTS
Tests are ordered based upon the child’s history, examination findings, and seizure description. Refer to Appendix D for normal values and/or ranges of laboratory and diagnostic tests.
1. Complete blood cell count (CBC)—to rule out infection or possible side effects to medication or ketogenic diet–like anemias or bleeding issues
2. Electrolyte panel—to look for possible metabolic or electrolyte causes
3. Urine and serum toxicology screens—to rule out ingestion as possible cause
4. Lumbar puncture—to rule out infection if febrile or concerned about possible meningitis or encephalitis
5. Antiepileptic drug levels—trough level is done to evaluate adherence to plan of care, to determine whether level medication is effective, or to ascertain peak level to determine reasons for side effects or toxicity
6. Urine organic acids and/or serum quantitative amino acids—to detect inborn errors of metabolism as possible cause
7. Routine electroencephalogram (EEG)—standard test for nonfebrile seizure to determine seizure type, epilepsy syndrome, and risk for recurrence; it assists in treatment management decisions. A normal EEG does not rule out epilepsy, and an abnormal EEG does not confirm it. An EEG is a guide for diagnosis and treatment decisions. The EEG is usually done at least 48 hours after the seizure so as not to confuse the findings with postictal slowing. An EEG is usually performed in partially sleep-deprived children to assist in detecting any abnormalities. If possible, the EEG should be done without sedation.
8. Video-EEG: provides video recording of the patient simultaneous with an EEG—to assist in comparing the clinical symptoms with electrographic changes on EEG during the clinical event. It further aids in determining the seizure type and possible epilepsy syndrome. This test is typically used when evaluating treatment failure and/or evaluating a possible candidate for epilepsy surgery.
9. Computed tomography (CT) of the brain—may be done as an emergent scan for quick determination of signs like bleeding, trauma, or tumor when the patient has postictal focal deficits or has not returned to baseline after the seizure.
